Functional improvements to implantable or insertable medical devices can be achieved by coating the surface of the device. For example, a coating formed on the surface of the device can provide improved lubricity, improved biocompatibility, or drug delivery properties to the surface. In turn, this can improve movement of the device in the body, extend the functional life of the device, or treat a medical condition near the site of implantation. However, various challenges exist for the design and use of coating apparatus designed to provide coatings to medical devices.
Traditional coating methods, such as dip coating, are often undesirable as they may result in flawed coatings that could compromise the function of the device or present problems during use. These methods can also result in coating inaccuracies, which can be manifested in variable amounts of the coated material being deposited on the surface of the device. When a drug is included in the coating material, it is often necessary to deliver precise amounts of the agent to the surface of the device to ensure that a subject receiving the coated device receives a proper dose of the agent. It has been difficult to achieve a great degree of accuracy using traditional coating methods and machines.
As another challenge, implantable or insertable medical devices are typically small and often have unusual, complex configurations. As a general matter, the handing of these devices in an appropriate manner during a coating procedure is often challenging.
Spray coating techniques have been used to apply coating material to various devices, including medical devices. See, for example, U.S. Pat. Nos. 6,562,136, 7,077,910, 7,125,577, and 7,192,484. In some cases, a coating process involves repetitively applying a coating material to a fixtured device in order to achieve a target quantity and quality of coated material. Devices are often manipulated between the applications of the coating material and dried to a certain extent before these manipulations are performed. It is often difficult to fixture and manipulate the devices so they receive a desired coating of material. It is also often difficult to prevent the coating apparatus and method from introducing defects into the formed coating.
One type of insertable medical device is a balloon catheter. Balloon catheter constructions are well known in the art and are described in various documents, for example, U.S. Pat. Nos. 4,195,637, 5,041,089, 5,087,246, 5,318,587, 5,382,234, 5,571,089, 5,776,101, 5,807,331, 5,882,336, 6,394,995, 6,517,515, 6,623,504, 6,896,842, and 7,163,523. Balloon catheters generally include four portions, the balloon, catheter shaft, guidewire, and manifold. A balloon catheter generally includes an elongated catheter shaft with an inflatable balloon attached to a distal section of the catheter shaft. At a proximal end of the catheter shaft, there is typically a manifold. At the manifold end, placement of the catheter can be facilitated using a guidewire. Guidewires are small and maneuverable when inserted into an artery. Once the guidewire is moved to the target location, the catheter with balloon portion is then fed over the guidewire until the balloon reaches the target location in the vessel. The balloon is typically inserted into the arterial lumen of a patient and advanced through the lumen in an unexpanded state. The balloon is then inflated when the catheter reaches target site resulting in application of mechanical force sufficient to cause vessel dilation. The balloon is typically inflated using a fluid, which is injected through an inflation port. The manifold can control the fluid introduction within shaft for expansion of the balloon. The mechanics of fluid transfer and introduction within balloons vary according to the specific design of the catheter, and are well know in the art.
Applicants have found that the complex design of a balloon catheter has made the balloon portion of the catheter difficult to coat. Accordingly, Applicants have provided new equipment and methods useful for overcoming the problems associated with the spray coating of medical devices, such as balloon catheters.